How do you know when to replace your alternator?
- Thread starter ShuggsRR
- Start date
jjorgensen52
NHSTE - I'm the only one!
Re: How do you know when to replace your alternator?
Well, my alternator started alternately charging and not charging to the point that the truck was almost impossible to drive long distance.... I've also had one die without warning, just pop and it was gone
Well, my alternator started alternately charging and not charging to the point that the truck was almost impossible to drive long distance.... I've also had one die without warning, just pop and it was gone
WyoSyclone
Active member
Re: How do you know when to replace your alternator?
If you can get it running, check the system voltage - it should be up around 13 volts to 13.8. If it's down around 12 the alternator is not charging (bad alt, or bad sense wire).
Take the battery down to a local auto parts store and have them do a load test on it (has to be charged before you do this). This will tell you if the battery is bad.
If you can get it running, check the system voltage - it should be up around 13 volts to 13.8. If it's down around 12 the alternator is not charging (bad alt, or bad sense wire).
Take the battery down to a local auto parts store and have them do a load test on it (has to be charged before you do this). This will tell you if the battery is bad.
sytyguy
Moderated User
Re: How do you know when to replace your alternator?
It would be best to have a load test done, but you can test voltage and amperage and make an educated guess. Test at the following conditions:
- Test battery with vehicle off (unhook cables if surface charge is detected)
- Idle - no headlights
- Idle - headlights on
- Rev to 2000 rpms - no headlights
- Rev to 2000 rpms - headlights on
You want as little change in between these (running) conditions as possible. If you're getting 13.5v at idle and cutting the headlights on causes a drop to 12.5v, then you've got an issue somewhere.
You want at least 13v (prefer 13.5-13.8), within 10% of rated battery amperage (60 amps above or below on a 600 amp battery is acceptable), within 10% of rated alternator amperage (10 amps above or below on a 100 amp alternator is acceptable).
HTHs
Hood
It would be best to have a load test done, but you can test voltage and amperage and make an educated guess. Test at the following conditions:
- Test battery with vehicle off (unhook cables if surface charge is detected)
- Idle - no headlights
- Idle - headlights on
- Rev to 2000 rpms - no headlights
- Rev to 2000 rpms - headlights on
You want as little change in between these (running) conditions as possible. If you're getting 13.5v at idle and cutting the headlights on causes a drop to 12.5v, then you've got an issue somewhere.
You want at least 13v (prefer 13.5-13.8), within 10% of rated battery amperage (60 amps above or below on a 600 amp battery is acceptable), within 10% of rated alternator amperage (10 amps above or below on a 100 amp alternator is acceptable).
HTHs
Hood
Don W.
Stab it and steer it
Re: How do you know when to replace your alternator?
Voltage tests are great and easy. Amperage tests are problematic without a reliable amp-meter. IMHO, since the alt is easy to remove just pull the thing and take it to a reputable shop and have it tested. End of doubt.
Have you checked the fuseable links? (In the wires near the back of the alt.)
Voltage tests are great and easy. Amperage tests are problematic without a reliable amp-meter. IMHO, since the alt is easy to remove just pull the thing and take it to a reputable shop and have it tested. End of doubt.
Have you checked the fuseable links? (In the wires near the back of the alt.)
QWERTYphoon
Motley Driver Award 2009
Re: How do you know when to replace your alternator?
All my alternators have made horrible noises before they go, any high pitched wining? I have one for sale I can bring to NATS!
All my alternators have made horrible noises before they go, any high pitched wining? I have one for sale I can bring to NATS!
Lynn D. Brown
New member
Re: How do you know when to replace your alternator?
What they said - Damn U guys are bright.
What they said - Damn U guys are bright.